title: Spindle pole body history intrinsically links pole identity with asymmetric fate in budding yeast.
abstract: BACKGROUND
  Budding yeast is a unique model for exploring differential fate in a cell dividing asymmetrically. In yeast, spindle orientation begins with the old spindle pole body (SPB) (from the preceding cell cycle) contacting the bud by its existing astral microtubules (aMTs) while the new pole delays astral microtubule organization. This appears to prime the inheritance of the old pole by the bud. The basis for this asymmetry and the discrimination of the poles by virtue of their history remain a mystery.
  
  
  RESULTS
  Here, we report that asymmetric aMT organization stems from an outstanding structural asymmetry linked to the SPB cycle. We show that the γ-tubulin nucleation complex (γTC) favors the old spindle pole, an asymmetry inherent to the outer plaque (the cytoplasmic face of the SPB). Indeed, Spc72 (the receptor for the γTC) is acquired by the new SPB outer plaque partway through spindle assembly. The significance of this asymmetry was explored in cells expressing an Spc72(1-276)-Cnm67 fusion that forced symmetric nucleation at the SPB outer plaques. This manipulation triggered simultaneous aMT organization by both spindle poles from the outset and led to symmetric contacts between poles and the bud, effectively disrupting the program for spindle polarity. Temporally symmetric aMT organization perturbed Kar9 polarization by randomizing the choice of the pole to be guided toward the bud. Accordingly, the pattern of SPB inheritance was also randomized.
  
  
  CONCLUSIONS
  Spc72 differential recruitment imparting asymmetric aMT organization represents the most upstream determinant linking SPB historical identity and fate.
authors.affiliation: Department of Genetics, University of Cambridge, Downing Street, Cambridge CB2 3EH, UK.
authors.forename: M Angeles
authors.initials: MA
authors.lastname: Juanes
authors.forename: Hanlu
authors.initials: H
authors.lastname: Twyman
authors.forename: Edward
authors.initials: E
authors.lastname: Tunnacliffe
authors.forename: Zhiang
authors.initials: Z
authors.lastname: Guo
authors.forename: Rogier
authors.initials: R
authors.lastname: ten Hoopen
authors.forename: Marisa
authors.initials: M
authors.lastname: Segal
mesh_terms: D002455:Cell Division; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D016133:Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D064047:Spindle Poles / Q000378:metabolism*; D014404:Tubulin / Q000235:genetics / Q000378:metabolism
chemical_list: C432934:Cnm67 protein, S cerevisiae; D003598:Cytoskeletal Proteins; C110443:KAR9 protein, S cerevisiae; D008869:Microtubule-Associated Proteins; D009687:Nuclear Proteins; C418484:SPC72 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014404:Tubulin